In forming a power distribution system it is necessary to provide means for a hot line carrying power to the required load and a return line to the power source. In a typical power distribution system for an integrated circuit logic system as many as ten interconnections may be required. There are connections between power supply and bus bar, bus bar and a mother board, a mother board and the daughter board, and connections between the daughter board and socket in which chips are usually mounted and a connection between the socket and an actual integrated circuit. Thus there are five points of interconnection in the line going from the hot terminal to the load and another five points of interconnection complete the return line of the circuit. In many integrated circuit systems there can be no more than 250 millivolts of drop in the voltage at each load. Some logic systems furthermore require multiple voltage power distribution systems. These systems therefore require electrical connectors or contacts that will minimize voltage drops as the load is placed on the system.
The speed at which the systems are operated is continually being increased as technology advances. To accommodate the ever quickening rate of change in the current draw, power distribution systems were generally provided with capacitors mounted on the various boards to store current that would be readily available as the demands from the load change. This lumped element method presents problems in that there is insufficient space available to accommodate larger capacitors required for higher speed logic families or higher rates of change in current demand.
To overcome problems associated with the earlier systems, it is desirable that power distribution systems be designed that are essentially equivalent to distributed element tuned circuits or transmission lines. By making a wide bus bar or conductor and by placing the hot and return conductors in close proximity such as forming a laminated bus bar, a high distributed capacitance can be achieved. This construction also gives a low resistance R, and inductance L. The bussing structure itself becomes a capacitor C and stores a large amount of the current that is needed to accommodate the rapidly changing load and in addition the current is distributed along the length of the entire bus structure. To minimize the distance between adjacent conductive layers, a very thin insulative layer is disposed between them to form a capacitive element and to prevent arcing.
One problem associated with laminated bus bars, however, is the inability to use standard two sided receptacle contacts to interconnect the laminated bus bar with another or to terminate to the laminated bus bar since a standard contact will electrically short the outer most conductive layers of the bus bar. Typically interconnections to laminated bus bars are made by providing the bus bar layers with tabs that extend outwardly from the various layers to which a wire or contact may be bolted to one voltage or layer. Since the wide bus bars are good conductors of heat as well as electricity, it is extremely difficult to achieve effective connections to the bus bar by soldering techniques. U.S. Pat. Nos. 3,400,303 and 3,893,233 disclose means for providing tabs and contact arrangements for providing input, output and ground connection to such laminated bus bars, one layer at a time. In addition to requiring bolted type connections or the like the use of tabs also prevents a controlled impedance system characteristic of tuned circuits and transmission lines. It is desirable therefore to provide a means for connecting to a laminated bus bar system that essentially controls any changes in the impedance of the system such as is required by high speed systems.
Furthermore it is desirable to have a separately means for connecting to the laminated bus bar system that retains the "plugability" of the system.
U.S. Pat. App. Ser. No. 07/169,514 filed Mar. 17, 1988 and assigned to the assignee hereof discloses a receptacle terminal for severable interface for power interconnection to a single layer bus bar. The terminal is comprised of a stamped and formed member having opposing spring arms which together act as a flared receptacle to receive a thick planar along the bus bar therebetween. The bus bar engages contact sections of the spring arms and deflects the stiff spring arms outwardly thereby generating a sufficient contact normal force between the terminal and the bus bar. The terminal further includes a pair of opposed plate sections joined by a lateral bite extending rearwardly from the spring arms and having an aperture extending therefrom for providing connection to a conventional ring tongue terminal terminated to a power cable. U.S. Patent No. 4,684,191 discloses a similar terminal comprising two cast metal members having arrays of opposed contact arms. The terminal is connected to a conventional ring tongue terminal terminated to a power cable. While the previously described terminals are suitable for connecting to bus bars, the bus bars are ones that comprise a single unit carrying a single voltage. These terminals are unsuitable for use with laminated bus bars since they would provide an electrical connection or short between the outer conductive layers of the laminated bus bar.